Spread out the okara on a plate lined with a paper towel. Microwave at 600 W for 2 minutes, mix, and microwave for another 2 minutes. Its weight should reduce from 100 g to 75 g.
Line a baking pan with parchment paper. Preheat the oven to 180℃.
Add the ingredients into a bowl and mix well.
Pour in batter into the pan. It is rather thick, so spread it out to an even thickness.
Top with walnuts.
Bake at 180℃ for 20 minutes.
Remove from oven, and once cooled, cut into whatever sized pieces you like. Sprinkle on some powdered sugar to finish.
Story Behind this Recipe
I ended up with some leftover okara when I made a "uno-hana" (a stir-fry of okara and vegetables) so I put it into brownies. Recommended for when you're dieting, since they're very chewy and filling. I use a rather modest amount of oil and sugar to help keep the calories down.
You evaporate the liquid from the okara by microwaving it. This makes it dry and easy to mix, and the distinctive orkara smell becomes less pungent.